Cancer immunotherapies have unique toxicities, and establishing toxicity grading scales and standardized grade-based treatment algorithms can improve the safety of these treatments. We have observed a toxicity syndrome, distinct from the more commonly observed cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), in patients treated with cell therapies for tumors in the central nervous system (CNS), which we term tumor inflammation-associated neurotoxicity (TIAN). TIAN is relevant not only to cellular therapies, but also to other immunotherapies for CNS tumors. To facilitate the safe administration of cell therapies for patients with CNS tumors, we define TIAN, propose a toxicity grading scale for TIAN syndrome and discuss the potential management of TIAN, with the goal of standardizing both reporting and management.